NERVOUS SYSTEM. 



585 



pular branch, abundantly restore the circula- 

 tion. Should the carotid have been tied, its 

 mesial communications, already mentioned, es- 

 pecially those within the skull, and about the 

 thyroid gland, assisted at those places and 

 elsewhere by anastomoses with the subclavian, 

 adequately fulfil their vicarious duty. So 

 abundant are these various communications, 

 that the ligature of a main trunk, in the dead 

 subject, in no degree interferes with the dis- 

 tension of its branches by fine injection : if we 

 inject water, or any equally fluid material, 

 through one carotid artery, it freely returns by 

 the oilier. Under these circumstances, it ex- 

 cites our surprise that the cure of aneurism by 

 ligature should be so certain ; for the amount 

 of circulation through the affected vessel can at 

 first be little affected, and the arrest and ulti- 

 mate cure of the disease must be referred rather 

 to the withdrawal of a distensive impulse than 

 to any considerable derivation of current. It 

 seems to have been considered, in operating 

 for aneurism, that, so long as no large branch 

 arose from the vessel closely on the cardiac 

 side of the ligature, it mattered not what 

 branches might arise on its distal side, how 

 large, or how near. In many instances secon- 

 dary haemorrhage, inducing death, has mani- 

 festly depended on defective adhesion at the 

 distal side of the ligature, and for an ob- 

 vious reason. The condition of that part of the 

 artery has been neglected : it has been thought 

 unimportant though a large vessel should arise 

 just beyond the ligature ; or, if a great length 

 of artery have been injudiciously denuded, the 

 cardiac portion has had an exclusive preference 

 of security given to it, by the ligature being 

 drawn as high as possible in that direction. 

 If an equal attention were bestowed on both 

 sides of the proposed seat of ligature, if like 

 care were taken, in both directions, to avoid 

 the likelihood of disturbance to the adhesive 

 process by side currents, if, where the artery 

 has been much denuded, (instead of a single 

 thread being applied at the cardiac extremity 

 of that isolated portion, by which plan the 

 succeeding part of the tube, though sepa- 

 rated from its connexions, and likely to ulce- 

 rate or slough, is yet left open to the stream 

 of recurrent blood,) a second ligature were 

 placed at the distal limit of the endangered 

 part, there would seem no greater reason to 

 anticipate the occurrence of secondary hsemor- 

 rhage than when arteries are tied after an am- 

 putation. 



3. Anomalous arrangement of the cervical 

 vessels is a contingency which the surgeon 

 must bear in mind Most of these are com- 

 prehended in the abnormalities of the arch 

 already described. (See AORTA.) The ex- 

 istence of a median interior thyroid artery, de- 

 rived from the arch, or from the arteria inno- 

 minala ; the irregular passage of the right 

 subclavian artery from the left side, behind the 

 oesophagus, or between that tube and the tra- 

 chea; an early division of the carotid, even 

 to nearly the level of the sternum, or so late a 

 one, that the common trunk furnishes many, 

 or most, of the branches normally originating 



from the external ; the absence of an arteria 

 innominata, its branches arising separately 

 from the arch, or in irregular combination with 

 those of the left side ; the occasional origin of 

 the vertebral from the common carotid,* are 

 the deviations which it most behoves the prac- 

 titioner to remember. 



4. Certain veins in the neck have an anato- 

 mical disposition, rendering them liable, when 

 opened in surgical operations, to become chan- 

 nels for inspiration of air to the cavities of the 

 heart, the fatal tendency of which is well 

 known. The internal jugular, innominata?, and 

 subclavian veins are, as M. Berard notices, 

 " at the root of the neck, so firmly united by 

 fascial laminae and cords to the adjacent bones 

 and muscles, that they do not collapse on divi- 

 sion, but gape:" and it is obvious that this cir- 

 cumstance (but for which they would be flat- 

 tened, and rendered impervious, by the atmo- 

 spheric pressure on their outward surface) must 

 expose them remarkably (perhaps alone) to a 

 dangerous participation in the inhuustive move- 

 ments of breathing. M. Velpeau (who has 

 written a paper of excellent critical research on 

 the subjectf) recommends the following pre- 

 cautions in approaching veins of the nature 

 described (vctnes canalis'ees) : studiously to 

 avoid wounding them, to detach no deeply 

 fixed tumour from its adhesions, without 

 having previously commanded the vessels at 

 its base, and to maintain no unnecessary ten- 

 sion on the fasciae, by forced positions of the 

 shoulder. 



For the BIBLIOGRAPHY see that of ANATOMY 

 (INTRODUCTION), and the references under the 

 various articles referred to. One work may be 

 particularized, as belonging to the region, and --is 

 having, more than any book of the age, given an 

 impetus to the study of anatomy in that most prac- 

 tical form, which interests the surgeon by unfolding 

 the relations of disease and of operative measures. 

 Through the happy combination referred to, the 

 mere barren description of regions has become 

 surgical anatomy ; and to Dr. Colles of Dublin, and 

 Alian Burns of Glasgow, belongs the merit of 

 having, first in this country, illustrated that natural 

 connexion, which gives to anatomy the interest of 

 application, and to practice the security of know- 

 ledge. 



(John Simon.) 



NERVOUS SYSTEM. In proportion as 

 our knowledge of the intimate texture of ani- 

 mal and vegetable organisms advances, the 

 doctrine gains ground that many of the phe- 

 nomena, called vital, are to be attributed to 

 the special endowments of distinct forms of 

 animal or vegetable matter ; distinct as regards 

 their anatomical characters as well as their 

 chemical composition ; distinct, therefore, as 



* A single instance has occurred to me in the 

 dissecting-room, of an arrangement, which I believe 

 to be very rare. An innominata (for so its origin 

 and course entitled it to be named) divided at the 

 sterno-clavicular joint into common carotid and 

 vertebral: the right subclavian arose from the de- 

 scending part of the arch, and directed itself to the 

 scalene space by passing behind the oesophagus. 



f Mcdecine Operatoire ; and Lettre sur 1'Intro- 

 duclioii dc 1'Air dans Ics Vcincs. Paris, 1838. 



